Polycarbonate resin molded articles have been widely used as, for example, industrial transparent materials in the fields of electrical and electronic engineering, mechanical engineering, automobiles, and the like or optical materials for lenses, optical disks, and the like because each of the articles is excellent in transparency and mechanical properties. When an additionally high mechanical properties is needed, a glass filler or the like is added to each of the articles to reinforce the article.
Glass fibers each constituted of glass generally called an E glass have been used as the glass filler. However, the refractive index of the E glass at a sodium D-line (nD, hereinafter simply referred to as “refractive index”) is somewhat small, specifically, about 1.555, though the refractive index of a polycarbonate resin is 1.580 to 1.590. Accordingly, when the glass filler is added to a polycarbonate resin composition in an amount needed for an increase in mechanical properties of the composition, the following problem arises: the resultant E glass-reinforced polycarbonate resin composition cannot maintain its transparency owing to a difference in refractive index between the filler and the polycarbonate resin of which the composition is formed, with the result that when the resin to which glossy particles are added in order that a metallic appearance or galactic appearance may be obtained is not the transparent resin, only the glossy particles near the surface of a molded article are seen, so neither a metallic appearance nor a galactic appearance can be obtained.
To solve such problem, investigation has been conducted on, for example, a reduction in refractive index of a polycarbonate resin by the improvement of the resin or an increase in refractive index of a glass filler by the improvement of the composition of the glass filler.
For example, (1) a resin composition containing a polycarbonate resin composition using a product of a reaction between a hydroxyaralkyl alcohol and a lactone as a terminating agent and a glass filler having a difference in refractive index of 0.01 or less from the polycarbonate resin composition (see Patent Document 1), (2) a resin composition formed of a polycarbonate resin, a glass filler having a difference in refractive index of 0.015 or less from the polycarbonate resin, and polycaprolactone (see Patent Document 2), and (3) a glass composition obtained by incorporating, for example, ZrO2, TiO2, BaO, and ZnO into a glass filler composition at a specific ratio so that the refractive index of the composition is close to that of a polycarbonate resin (see Patent Document 3) have been proposed.
However, the resin composition in Patent Document 1 is not practical because of the following reasons: when the glass filler is added in an amount needed for improvement in dimensional stability and mechanical properties of the composition, the difference in refractive index at such level is not small enough for the addition to exert its effect, and the glass filler is too expensive to be used as a raw material for the production of the polycarbonate resin composition.
The polycarbonate resin composition in Patent Document 2 involves the following problem: reductions in heat resistance and mechanical properties of the composition are inevitable owing to the presence of polycaprolactone which has a low softening temperature and is added to decrease the refractive index, though the composition can maintain its transparency even when the glass filler has a difference in refractive index of 0.015 or less from the polycarbonate resin.
Unless the content of each of, for example, ZrO2, TiO2, BaO, and ZnO in the glass composition in Patent Document 3 is appropriately adjusted, the glass filler itself will devitrify. As a result, even when the glass filler composition has a refractive index almost equal to that of the polycarbonate resin, a polycarbonate resin composition containing the glass filler composition may be unable to obtain transparency. In addition, the significance of the use of a glass filler-reinforced polycarbonate resin composition for the purpose of a weight reduction wanes because the specific gravity of the glass filler itself increases. In addition, none of Patent Documents 1 to 3 make any mention of the problem of the decrease of the weld line and the decrease in orientation of the glossy particles.
Further, in the case of a polycarbonate resin composition containing glossy particles, when the resin composition is molded, a weld line is formed at a part where molten resin compositions are merged into and welded to each other, and as a result, the difference in lightness between the left and right sides of the weld line is caused.
As a result of this phenomenon, light reflection by the glossy particles is scattered, and accordingly, the vicinity of the weld line becomes dark. Accordingly, there lowers a commercial value of a resin molded article, and hence there have been proposed various conutermeasures to prevent the phenomenon.
For example, as the glossy particles, there have been proposed: (4) a resin composition containing particles having a shape in which an average particle diameter is 10 to 300 μm and an aspect ratio is ⅛ to 1 (see Patent Document 4); and (5) a resin composition containing fine metal particles which is in a square shape with a notch at one corner (see Patent Document 5). In those glossy particles, it has been suggested that the shapes of the glossy particles themselves can prevent formation of the weld line and have an effect of decreasing the orientation of the glossy particles.
However, in Patent Documents 4 and 5, there is no description about the case of adding a glass filler to the resin composition, and, as might be expected, there is no description that the orientation of the glossy particles can be decreased by the glass filler. In addition, there is no description on flame retardancy of the resin composition, and the fields in which the resin composition can be used are limited when flame retardancy is not imparted thereto.
It should be noted that (6) a glass-filler-reinforced polycarbonate resin composition having a metallic appearance (see Patent Document 6) has been also proposed, but in this case, there is no description on an issue of decreasing the orientation of the glossy particles on the weld line. In addition, there is no description on flame retardancy of the glass-filler-reinforced polycarbonate resin composition, and the fields in which the glass-filler-reinforced polycarbonate resin composition can be used are limited when the flame retardancy is not imparted thereto.
Further, there has been disclosed (7) a molded product in which amorphous polymer particles are attached to flaky fine particles by performing precipitation polymerization of a polycarbonate-based resin and the like in the presence of glossy flaky fine particles in order not to cause appearances defects such as a weld line and a weld dichroism (see Patent Document 7).
Still further, there has been proposed (8) a polycarbonate resin composition, in which a refractive index is improved by adding thereto a polycarbonate resin and a specific glass to which oxides of various metals are added, and which has a difference in refractive index of 0.001 or less from the polycarbonate resin composition (see Patent Document 8).
However, in the case of Patent Document 7, it is only AAS resin that is specifically described as the amorphous polymer in examples and comparative examples, and there is no description about the polycarbonate resin. In addition, there is no description about the case of adding a glass filler to the polycarbonate resin, and, as might be expected, there is no description that the orientation of the glossy particles can be decreased by the glass filler. There is also no description on flame retardancy of the polycarbonate resin, and the fields in which the polycarbonate resin can be used are limited when flame retardancy is not imparted thereto. In the polycarbonate resin composition of Patent Document 8, there is no description on an issue of decreasing the orientation of the glossy particles on the weld line, and in addition, there is no reference to flame retardancy of the polycarbonate resin composition, and the fields in which the polycarbonate resin composition can be used are limited when flame retardancy is not imparted thereto.    Patent Document 1: JP07-118514-A    Patent Document 2: JP09-165506-A    Patent Document 3: JP05-155638-A    Patent Document 4: JP06-99594-A    Patent Document 5: JP07-53768-A    Patent Document 6: JP06-212068-A    Patent Document 7: JP2001-262003-A    Patent Document 8: JP2006-022236-A